Such compressors are well-known and generally comprise an electric motor which drives a suitable air compressor using the electrical energy from the vehicle's own electrical supply system. This is usually achieved by means of a plug which can fit into the cigar lighter of a vehicle to connect the compressor to the vehicle's battery.
A pressure gauge can be provided on the outlet line from the compressor so that the user can judge the air pressure which the tire is being inflated. This requires careful attention on the part of the user, however, to watch the pressure and ensure that he stops the inflation at the right moment.
It is an object of the present invention to avoid this problem and to allow the user to pre-set a desired inflation pressure and have the compressor stop at that point.